Acute cerebellitis with a reversible splenial lesion in a pediatric patient with influenza

Influenza cerebellitis is an extremely rare disease with limited understanding of its clinical course, treatment, and neurological outcomes. An 8-year-old girl presented with fever and was diagnosed with type A influenza. She later developed altered mental status on day three, leading to hospitalization on day four. Upon hospitalization, cerebrospinal fluid (CSF) analysis revealed increased white blood cell counts and protein levels, and magnetic resonance imaging (MRI) showed high-intensity signals at the splenium of the corpus callosum (SCC), suggestive of mild encephalitis/encephalopathy with a reversible splenial lesion. However, arterial spin labeling (ASL) revealed increased cerebellar blood flow, raising suspicion of acute cerebellitis. Intravenous methylprednisolone pulse therapy was administered. Despite fever resolution, the patient's impaired consciousness persisted. MRI on day eight showed new lesions in the bilateral cerebellar hemisphere, white matter, and dentate nuclei instead of splenial lesion disappearance, suggesting acute cerebellitis. The patient received intravenous immunoglobulin G and repeated methylprednisolone pulse therapy, which led to gradual improvement. MRI on day 32 revealed lesion resolution. The patient was discharged with neurological sequelae (dysarthria and slight dysmetria), which improved completely after two months. This is the second reported pediatric case of influenza cerebellitis with a reversible SCC lesion, which presented with atypical neutrophilic pleocytosis on CSF analysis and unique findings on initial MRI. This case highlights the importance of early diagnosis and treatment of influenza cerebellitis. Repeat MRI, including ASL, should be considered in suspected cases of influenza-related encephalitis/encephalopathy. Further research is needed to establish optimal diagnostic and treatment strategies for influenza cerebellitis.